A variety of pump dispensers are available for dispensing a number of products in the form of atomized liquid. To dispense liquid, the liquid which is stored in the container must pass through a valve in order to enter a passageway which communicates with a discharge opening.
In conventional dispensers, a seal is formed between two members to block the passageway when the dispenser is closed, and to open the passageway to permit liquid to be dispensed when the dispenser is in the open position. A number of prior art patents disclose a pair of essentially non-deformable members that sealingly engage one another to block the passageway when the dispenser at rest, and which are mechanically moved apart from one another to open the passageway to dispense liquid. See, for example, U.S. Pat. Nos. 4,050,860 to Beres and 4,063,854 to Hayes et al.
Other patents, such as U.S. Pat. No. 3,949,910 to Focht, disclose an arrangement in which a seal has a fixed edge and an opposite free portion which is mechanically moved from a discharge passageway-closed position and a discharge passageway-open position.
The arrangements disclosed in those patents are disadvantageous in that the members are mechanically moved out of engagement with each other when moving from the closed to the open position, and are mechanically held apart while maintaining the open position. This is disadvantageous in that the passageway may be open even when there is insufficient pressure for dispensing liquid; it is only after the members are mechanically moved to the closed position that the passageway is again sealed closed.
Another arrangement is shown in U.S. Pat. No. 3,940,028 to Beard wherein a seal closes the passageway in the closed position, and the entire seal tilts and assumes a dish-shaped configuration in the open position to permit liquid to be dispensed. The Beard arrangement is also disadvantageous because the passageway tends to remain open until the members are mechanically moved to the closed position.